1. Field of the Invention
The present invention relates to an improvement of a power unit supporting structure of a scooter type vehicle.
2. Description of Background Art
Heretofore, on the power unit supporting structure of a scooter type vehicle, one in which a power unit provided with a balancer shaft is swingably attached to the vehicle frame through a link is known (for example, refer to Japanese Patent Application Laid-open No. 2003-237674.
As shown in FIGS. 14 and 15 of Japanese Patent Application Laid-open No. 2003-237674, a power unit 3, which drives a rear wheel 2, is swingably attached to a vehicle frame 4 through a link 5.
One end of the link 5 is connected to damper rubber assemblies 64 and 65 with supporting shafts 61 and 62, the damper rubber assemblies 64 and 65 being attached to two cylindrical bosses 51 and 52 on the side of the vehicle frame 4; and the other end of the link 5 is connected to an upper portion of the power unit 3 with a supporting shaft 63.
The link 5 extends roughly along an imaginary line L extending from a contacting point P of the rear wheel 2 through the center of gravity G of a power unit 3. In addition, the direction of a vibration of the power unit 3 is perpendicular to the link 5, the vibration thereof being caused by a coupling force which occurs due to the distance between a crankshaft 16 and a balancer 17 when the engine is in operation. For these reasons, the above vibration of the power unit 3 can be effectively damped by the swinging of the link 5. However, when a secondary vibration in the direction of the cylinder axis of an engine 11 is occurs on the power unit 3, it is difficult to effectively reduce the above-mentioned secondary vibration, since the link 5 tilts to the direction of the cylinder axis.